Get the code: learn.COB
COBOL is a business-oriented language revised multiple times since its original design in 1960. It is claimed to still be used in over 80% of organizations.
*COBOL. Coding like it's 1985. *Compiles with GnuCOBOL in OpenCobolIDE 4.7.6. *COBOL has significant differences between legacy (COBOL-85) *and modern (COBOL-2002 and COBOL-2014) versions. *Legacy versions require columns 1-6 to be blank (they are used *to store the index number of the punched card). *A '*' in column 7 means a comment. *In legacy COBOL, a comment can only be a full line. *Modern COBOL doesn't require fixed columns and uses *> for *a comment, which can appear in the middle of a line. *Legacy COBOL also imposes a limit on maximum line length. *Keywords have to be in capitals in legacy COBOL, *but are case insensitive in modern. *Although modern COBOL allows you to use mixed-case characters *it is still common to use all caps when writing COBOL code. *This is what most professional COBOL developers do. *COBOL statements end with a period. *COBOL code is broken up into 4 divisions. *Those divisions, in order, are: *IDENTIFICATION DIVISION. *ENVIRONMENT DIVISION. *DATA DIVISION. *PROCEDURE DIVISION. *First, we must give our program an ID. *Identification division can include other values too, *but they are comments only. Program-id is the only one that is mandatory. IDENTIFICATION DIVISION. PROGRAM-ID. LEARN. AUTHOR. JOHN DOE. DATE-WRITTEN. 05/02/2020. *Let's declare some variables. *We do this in the WORKING-STORAGE section within the DATA DIVISION. *Each data item (aka variable) starts with a level number, *then the name of the item, followed by a picture clause *describing the type of data that the variable will contain. *Almost every COBOL programmer will abbreviate PICTURE as PIC. *A is for alphabetic, X is for alphanumeric, and 9 is for numeric. *example: 01 MYNAME PIC xxxxxxxxxx. *> A 10 character string. *But counting all those x's can lead to errors, *so the above code can, and should *be re-written as: 01 MYNAME PIC X(10). *Here are some more examples: 01 AGE PIC 9(3). *> A number up to 3 digits. 01 LAST_NAME PIC X(10). *> A string up to 10 characters. *In COBOL, multiple spaces are the same as a single space, so it is common *to use multiple spaces to line up your code so that it is easier for other *coders to read. 01 inyear picture s9(7). *> S makes number signed. *> Brackets indicate 7 repeats of 9, *> ie a 6 digit number (not an array). *Now let's write some code. Here is a simple, Hello World program. IDENTIFICATION DIVISION. PROGRAM-ID. HELLO. DATA DIVISION. WORKING-STORAGE SECTION. 01 THE-MESSAGE PIC X(20). PROCEDURE DIVISION. DISPLAY "STARTING PROGRAM". MOVE "HELLO WORLD" TO THE-MESSAGE. DISPLAY THE-MESSAGE. STOP RUN. *The above code will output: *STARTING PROGRAM *HELLO WORLD ********COBOL can perform math*************** ADD 1 TO AGE GIVING NEW-AGE. SUBTRACT 1 FROM COUNT. DIVIDE VAR-1 INTO VAR-2 GIVING VAR-3. COMPUTE TOTAL-COUNT = COUNT1 PLUS COUNT2. *********PERFORM******************** *The PERFORM keyword allows you to jump to another specified section of the code, *and then to return to the next executable *statement once the specified section of code is completed. *You must write the full word, PERFORM, you cannot abbreviate it. IDENTIFICATION DIVISION. PROGRAM-ID. HELLOCOBOL. PROCEDURE DIVISION. FIRST-PARA. DISPLAY 'THIS IS IN FIRST-PARA'. PERFORM THIRD-PARA THRU FOURTH-PARA. *>skip second-para and perform 3rd & 4th *> then after performing third and fourth, *> return here and continue the program until STOP RUN. SECOND-PARA. DISPLAY 'THIS IS IN SECOND-PARA'. STOP RUN. THIRD-PARA. DISPLAY 'THIS IS IN THIRD-PARA'. FOURTH-PARA. DISPLAY 'THIS IS IN FOURTH-PARA'. *When you compile and execute the above program, it produces the following result: THIS IS IN FIRST-PARA THIS IS IN THIRD-PARA THIS IS IN FOURTH-PARA THIS IS IN SECOND-PARA **********Combining variables together using STRING *********** *Now it is time to learn about two related COBOL verbs: string and unstring. *The string verb is used to concatenate, or put together, two or more strings. *Unstring is used, not surprisingly, to separate a *string into two or more smaller strings. *It is important that you remember to use ‘delimited by’ when you *are using string or unstring in your program. IDENTIFICATION DIVISION. PROGRAM-ID. LEARNING. ENVIRONMENT DIVISION. DATA DIVISION. WORKING-STORAGE SECTION. 01 FULL-NAME PIC X(20). 01 FIRST-NAME PIC X(13) VALUE "BOB GIBBERISH". 01 LAST-NAME PIC X(5) VALUE "COBB". PROCEDURE DIVISION. STRING FIRST-NAME DELIMITED BY SPACE " " LAST-NAME DELIMITED BY SIZE INTO FULL-NAME END-STRING. DISPLAY "THE FULL NAME IS: "FULL-NAME. STOP RUN. *The above code will output: THE FULL NAME IS: BOB COBB *Let’s examine it to see why. *First, we declared all of our variables, including the one that we are creating *by the string command, in the DATA DIVISION. *The action takes place down in the PROCEDURE DIVISION. *We start with the STRING keyword and end with END-STRING. In between we *list what we want to combine together into the larger, master variable. *Here, we are combining FIRST-NAME, a space, and LAST-NAME. *The DELIMITED BY phrase that follows FIRST-NAME and *LAST-NAME tells the program how much of each variable we want to capture. *DELIMITED BY SPACE tells the program to start at the beginning, *and capture the variable until it runs into a space. *DELIMITED BY SIZE tells the program to capture the full size of the variable. *Since we have DELIMITED BY SPACE after FIRST-NAME, the GIBBERISH part is ignored. *To make this clearer, change line 10 in the above code to: STRING FIRST-NAME DELIMITED BY SIZE *and then re-run the program. This time the output is: THE FULL NAME IS: BOB GIBBERISH COBB
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Originally contributed by Hyphz, and updated by 6 contributor(s).